The Lord’s Table is a table of community accountability. By God’s grace, our local church has not yet needed to remove anyone from fellowship due to church discipline. He has guarded our flock from gross, ongoing, unrepentant sinners. We have been able to enjoy the sweetness of communion without too much sadness.
This is fellowship worth preserving, worth protecting, and that means that not everyone is invited. In particular, when professing brothers refuse to repent from their sin after they have been personally, lovingly, and repeatedly pursued, they may be formally uninvited from participation.
The Lord requires one brother who sees another sinning brother to confront the sinner (Matthew 18:15). The Lord instructs more people to get involved if there is not repentance and, eventually, the (local) church must acknowledge the immorality and discipline the sinner by removing him from fellowship (Matthew 18:16-17). Those inside the church judge those inside the church (1 Corinthians 5:11-13). This is part of mutual accountability.
The church gets it wrong sometimes, more often than not by failing to deal with sinners. According to 1 Corinthians 11:29-32, God sometimes intervenes directly rather than through the church toward those who profane the body and blood of the Lord by unworthy participation at His Table. God is not mocked even if the church gets it wrong. Death is an even stronger statement about the value of the Lord’s Table than church discipline.
Of course, it is not much of a discipline to keep someone from something that we don’t value or enjoy. Our enjoyment of communion now sets the tone for later. The offender will miss out to the degree that we make much of this meal. We will give an account for how we participated, and it ought to be with righteous rejoicing.